1. Field of the Invention
The present invention relates to solar voltaic storage cells which are capable of generating and storing electrical energy due to the action of sunlight on a cell having a pair of electrodes immersed in certain types of metallic complex solutions. The invention also relates to novel carboxyl metallic and related organometallic complexes for use in the solar cells.
2. Background Information
Generation of electrical power in the United States involves a heavy dependence on fossil fuels and nuclear energy, both of which have serious environmental consequences which make these sources of energy less than desirable. Alternative sources of electrical energy, particularly solar electrical generators, have been developed for a cleaner production of electricity without the environmental hazards which are associated with nuclear and fossil fuel generators. A typical device for generating electricity from sunlight utilizes certain light sensitive chemicals in a solution having electrodes immersed therein. One such device which utilizes a solution of light sensitive chemical is disclosed in U.S. Pat. No. 4,190,705. U.S. Pat. No. 4,190,705 discloses a photogalvanic cell which produces electricity due to the interaction of light with a specific light sensitive solution within the cell having one-half cell exposed to light and the other half cell exposed to dark. The light sensitive solution is acidic and contains a dye such a thionine and a metal redox couple such as Fe.sup.+.spsp.2 /Fe.sup.+.spsp.3. Each half cell contains an electrode. The reaction at the electrode exposed to light is: Th+Fe.sup.+.spsp.2 .fwdarw.Fe.sup.+.spsp.3 +Th.sup.- and the reaction at the dark electrode is Fe.sup.+.spsp.3 +e.sup.- .fwdarw.Fe.sup.+.spsp.2.
When the half cells are electrically connected, a current flows from the electrode exposed to light to the electrode exposed to dark. However, a reverse reaction at the dark electrode diminishes the efficiency of the cell. The reverse reaction is: Fe.sup.+.spsp.3 +Th.sup.- .fwdarw.Fe.sup.+.spsp.2 +Th.
In order to minimize the loss of efficiency due to the reverse reaction, the reverse reaction is suppressed by adding a complexing agent to the solution. The reverse reaction is suppressed due to the formation of a complex with the higher valent ion (e.g., Fe.sup.+.spsp.3) of the redox complex. Suitable complexes for suppressing the reverse reaction are formed by adding fluoride ions, phosphate ions, citrate ions, oxalate ions or 2-amino-propionate ions to the cell containing the dye and redox couple.
It will be readily appreciated that certain deficiencies exist with respect to the device described in U.S. Pat. No. 4,190,705. Most notable, it will be observed that the device requires that one of the electrodes be kept in the dark while the other electrode is exposed to light. Such an arrangement requires a more complex structure to assure that light does not enter into one of the half cells. In addition, the device requires the presence of thionine to carry the charge to the electrode. The presence of thionine is disadvantageous because of the above described reverse reaction which takes place at the dark electrode.
Also, U.S. Pat. No. 4,190,705 utilizes iron complexes to suppress the reverse reaction. The iron complexes serve mainly to suppress this reaction and, although they result in an increase in power output due to the suppression of the reverse reaction, the total output still remains quite low in this device. It is believed that the complexes formed in the '705 patent are not very efficient due to poor complex formation.
Accordingly, a need exists in the art to provide a more efficient solar cell which avoids the deficiencies noted above with respect to U.S. Pat. No. 4,190,705.